What is the purpose of this article?
Provides an overview and general concepts of Rheonics DVM HPHT density and viscosity module sensor, covering its technical specifications, applications, installation, maintenance, and proper use in high-pressure and high-temperature environments.

What products are involved?
Rheonics DVM HPHT density viscosity module and DTCM Thermal Control Module

TABLE OF CONTENTS

• Introduction
• Sensor Description
• Mechanical Specifications
• Cleaning and Maintenance
• Applications and use cases

Introduction

The accuracy of a sensor is key in all industries to ensure reliable monitoring readings. Equally important is its robustness, ensuring that the expected accuracy is maintained even under harsh conditions such as High-Pressure and High-Temperature (HPHT) applications. An example of these requirements can be found in the Oil and Gas Industry, where hydrocarbon fluids are analyzed under extreme pressure and temperature ratings to optimize processes and ensure operational efficiency. However, traditional measurement methods often face limitations under these extreme conditions.

The DVM (Density, Viscosity Module) from Rheonics is a sensor designed to measure real-time fluid density, viscosity, and temperature simultaneously. Specially built to operate under high-pressure and high-temperature (HPHT) conditions, it withstands up to 2,100 bar (30,000 psi) of pressure and temperatures of up to 200°C (392°F), making it ideal for demanding industrial applications such as PVT (Pressure-Volume-Temperature) studies for hydrocarbons and reservoir fluids in the oil and gas industry. It enables fluid analysis with minimal sample requirements, as the DVM has an inner fluid volume of just 0.7 cc.

Figure 1. Rheonics DVM Sensor Unit

Here are some key features and advantages of the DVM Sensor Unit:

• Minimal Sample Requirement: Less than 0.7 cc of fluid is needed for measurements.
• Pressure Limit: Up to 2100 bar (30,000 psi) for HPHT applications. Requires correct configuration in ordeer.
• Temperature Limit: -40 °C to 200°C (392°F), ensuring reliable operation under extreme thermal conditions. Requires correct configuration in order.
• Integrated Pressure Compensation: A pressure gauge is required for high-pressure applications to maintain measurement accuracy and ensure reliable readings.
• MInimum maintenance: Clean module and sensor is required for accurate readings. Review section below for guidelines on maintenance and cleaning.
• Rapid Measurement Response: Provides measurement results in less than 2 seconds, facilitating real-time monitoring and control.
• Fluid Compatibility: Works with Newtonian and non-Newtonian fluids, as well as single-phase and multi-phase systems. Not suitable for fluids with magnetic particles.

Sensor Description

Specifications

The Rheonics DVM sensor is built to perform in extreme industrial environments, with high resistance to both pressure and temperature values, ensuring operation in demanding conditions.

Operating principle

Rheonics DVM is based on the balanced torsional resonator technology. A pair of sensing tips shears fluid, making the sensor sensitive to fluid density and viscosity changes. From the damping and resonant frequency of the resonator, the density and viscosity can be calculated using Rheonics' proprietary algorithms.

Figure 2. DVM sensing element principle.

Pressure compensation

Pressure compensation is required for accurate density and viscosity measurements at high pressures. Rheonics sensor electronics handle compensation internally but require an external pressure input. The pressure value (in bar) should be provided to the SME through one of the following methods:

• RCP Software: A fixed pressure value can be manually entered in RCP or received from an external pressure gauge via a LabVIEW driver. Rheonics supports certain pressure gauge drivers, with communication over a serial port. See the RCP Manual (RCP-OM).
  
• LabVIEW VI: Users can create or request a default LabVIEW VI from Rheonics to integrate a pressure gauge with the sensor. LabVIEW software is required. See the LabVIEW COM API manual (RAPI-OP).
  
• Modbus Communication: An external PLC can write the pressure value to the Modbus register. See the Modbus TCP (MTCP-OP) or Modbus RTU (MRTU-OP) manuals.

Find more information on:

• Configure Pressure Input for DV Sensor over Modbus RTU/TCP 
• External Pressure Sensor-How the library should be designed? 
• External Pressure Sensor-How does it work with the RCP software? 

Note: Rheonics does not supply the pressure gauge; this must be sourced by the client. Rheonics supports drivers for gauges from brands such as Additel, Keller, and Paroscientific.

Mechanical Specifications

Dimensions and Drawings

Dimensions overview

Figure 4. DVM module dimensions

Components and assembly

Figure 5. DVM Components

Internal DV Sensing Element

Figure 6. DV Sensing Element and internal sealing rings

Materials

All wetted parts of the DVM module are made of Titanium Grade 5, which is compatible with a wide range of chemical fluids. To ensure a leak-proof design under HPHT conditions, the sensor is equipped with two sealing rings, these are:

• A sealing O-ring made of FKM as standard material, AFLAS material available upon request. The O-ring material must be compatible with the fluid being measured to ensure optimal performance and durability.
• A backup ring, made of PEEK (Polyether Ether Ketone), designed to ensure sealing in HPHT environments.

Figure 3. DVM sensing element

Installation

The DVM unit is designed for inline installation as a flow-through cell instrument, measuring the density and viscosity of the fluid in contact with the DV sensor inside the module. Proper installation requires:

1. Ensure the whole sensing area is in contact with the fluid

The DV sensor has two parallel fins that must be fully immersed in the fluid. To ensure accurate and repeatable measurements, avoid deposits, solids, or magnetic particles from blocking the sensor.

Figure 7. DV sensing area

2. Proper orientation

The DVM should be mounted with the internal sensor facing downward, preventing air bubbles from affecting measurements. The recommended flow direction is with the inlet positioned lower than the outlet to allow trapped bubbles to collect at the sensor base, where they won't interfere with readings.

Figure 8. DVM recommended flow direction

The DVM module features 1/4" HP (9/16-18 UNF) female-threaded inlet and outlet ports. Users must connect adapters to these threads for proper integration into their process.

For convenience, Rheonics offers high-pressure fitting connectors, including:

• Collar
• Gland
• Tube (OD 1/4" - ID 1/8")

These high-pressure fittings follow industry standards and can also be sourced from suppliers such as HiP, Swagelok, or equivalent manufacturers.

For reference: https://www.highpressure.com/pdfs/section/hp.pdfHiP High-Pressure Equipment catalog

Cleaning and Maintenance

Proper cleaning and maintenance of the DVM sensor ensure long-term reliability and accuracy. The sensor is designed for minimal maintenance, but periodic cleaning may be necessary to remove fluid deposits and contamination.

Figure 9. DV sensor clean and with deposits

Removal of the DV sensor from the DV Module

Rheonics delivers the DVM unit with the DV sensor already installed. The client may need to remove the DV sensor for cleaning or maintenance. Follow the next steps to remove the DV sensor from the DV Module. Steps are also available in a tutorial video from Rheonics DVM Removing Sensing Element.

1. Loosen the Sensor Retaining Screw

• Use a torque wrench (such as the one provided by Rheonics) to remove the sensor retaining screw.
• Apply approximately 20 N·m of torque (TOW-DVM is rated for this).
• If needed, secure the DVM-HPHT in a bench vise using soft jaw covers to prevent damage.

2. Access the DV Sensor

• Removing the retaining screw reveals the back of the DV sensor, exposing its M4 threaded removal/insertion hole.

3. Attach the Removal Tool

• Use the sensor insertion and removal tool (ERT-DVM).
• While holding the black screw grip, screw the threaded rod into the M4 hole in the sensor until finger-tight.

4. Extract the Sensor

• Hold the back of the threaded rod and turn the black ring clockwise against the upper surface of the module.
• This action will back the sensor out of the module safely.

Cleaning considerations

Proper cleaning of the DVM sensing element and inner line in cell module is required to maintain accurate measurements. Any high-viscosity fluids, solid deposits, or magnetic particles adhering to the sensing element can distort readings.

Standard Cleaning Procedure

• Flush the System: Flow a solvent or cleaning fluid through the DVM module, followed by distilled water and then compressed air to remove residues.
• Baseline Check: Run the sensor in air or vacuum; the readings for density and viscosity should be zero, indicating a clean sensor.

Manual Cleaning Methods

• Solvent Cleaning: Remove the DV sensor and wipe it with a solvent-saturated cloth or immerse it in a beaker with solvents.
• Ultrasonic Bath: For small deposits, submerge the DV sensing element in an ultrasonic bath for 5–10 minutes. For heavy deposits, extend to 30–60 minutes.
• Magnetic Particle Removal: Use Scotch tape or masking tape to lift magnetic particles from the sensor surface. A magnifying lens can help verify cleanliness.

General Cleaning Guidelines

• Chemical Compatibility: Ensure that cleaning chemicals are compatible with all sensor materials.
• CIP (Clean-in-Place) Compatibility: The DVM is CIP-compatible, allowing inline cleaning.
• Sealing Component Maintenance: Inspect and replace the O-ring and backup ring if damaged, worn, or exposed to solvents like acetone.
• No Abrasives: Never use abrasives on the resonator, as this will alter its geometry and destroy calibration.
• Ultrasonic Cleaning Limitations: The DVM module itself should not be cleaned with an ultrasonic bath, only the DV sensing element.

Applications and use cases

Rheonics DVM Density and Viscosity Module sensor is built for different application cases where a real-time value of density, viscosity, and temperature are required in high-pressure and temperature applications, with minimal sample size needed.

PVT (Pressure-Volume-Temperature) analysis and core flooding studies

The Rheonics DVM sensor is widely used in PVT studies to analyze fluid behavior under different pressures and temperatures, providing real-time density and viscosity measurements in simulated reservoir conditions. It is also applied in core flooding experiments to evaluate fluid displacement efficiency. For more details, check our article: https://support.rheonics.com/en/support/solutions/articles/81000416189-using-rheonics-dvm-in-a-high-pressure-loop-setup-and-operation-guide

HPHT Fluid Analysis with Thermal Control

Rheonics DVM must always operate under controlled thermal conditions. This can be achieved either by placing it in an oven or by integrating it with the Rheonics DTCM Thermal Control Module, ensuring uniform heating and cooling for accurate fluid property measurements.

 For more details, check our article: https://support.rheonics.com/en/support/solutions/articles/81000413697-dtcm-hpht-dvm-simultaneous-density-viscosity-temperature-sensor-thermal-control-module

Others

• High-pressure diesel injector development.
• Lubricant viscosity profiling under operational HPHT conditions.
• Simulation of deepwater conditions. Pipeline and umbilical restart tests.
• Stability tests of emulsions for non-Newtonian and Newtonian fluids.

References

Rheonics DVM Manual

DTCM Thermal Control Module for DVM 

High Pressure Loop for DVM 

DTCM Support Article